Developments in miniaturization and large-scale integration in fluidics have led to the concept of creating an entire chemistry or biology laboratory on a fluidic analog of the electronic microchip. Such integrated microfluidic devices (known as Micro Total Analysis Systems, or μTAS) are seen as key to automating and reducing costs in many biological analysis applications, including genetic analyses and medical diagnostics. Unlike the microelectronics industry, there is no general consensus in the analytical instruments industry about the most appropriate technologies for μTAS devices. Some companies are building μTAS devices by etching small glass plates or silicon chips. Others are working with either hard or soft polymeric materials fabricated by injection molding or by hot embossing. Producing reliable valves has turned out to be problematic with both types of devices. In etched solid chips, the valves tend to be very complicated, requiring multiple etching and deposition steps, and they suffer from a tendency to leak. Valves are easier to make in soft materials but, so far, they have been actuated only by pneumatic pressure, which presents difficulties for controlling the valves.
Traditional fluid valves operate by moving solid objects to obstruct the flow path. This requires sealing against a valve seat, and often leads to complicated geometries. Pneumatic valves used on μTAS devices are typically made by crossing two flow channels with a thin flexible membrane between them. One of the flow channels acts as a control to switch the flow on and off in the other channel. This is done by pressurizing the control channel, which leads to a deformation of the membrane separating the two channels. With a sufficiently high pressure in the control channel, the membrane completely closes the other channel. While this method has been shown to work for some applications, there are issues with the large number of pneumatic control lines required for large-scale integrated μTAS devices, as well as with concerns about leakage, and the limitations on operating pressure.